diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 910a4da0a6..4594909242 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -2161,6 +2161,8 @@ static abi_long do_setsockopt(int sockfd, int level, int optname,
 
             QEMU_BUILD_BUG_ON(sizeof(struct ip_mreq) !=
                               sizeof(struct target_ip_mreq));
+            QEMU_BUILD_BUG_ON(sizeof(struct ip_mreqn) !=
+                              sizeof(struct target_ip_mreqn));
 
             if (optname == IP_MULTICAST_IF) {
                 min_size = sizeof(struct in_addr);
diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
index 6967306be4..5799769f83 100644
--- a/linux-user/syscall_defs.h
+++ b/linux-user/syscall_defs.h
@@ -210,7 +210,7 @@ struct target_ip_mreq {
 struct target_ip_mreqn {
     struct target_in_addr imr_multiaddr;
     struct target_in_addr imr_address;
-    abi_long imr_ifindex;
+    abi_int imr_ifindex;
 };
 
 struct target_ip_mreq_source {